Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.77	8.489%	$186.3516	$186.35	$186.35	$186.40
Purchase #2	$51.54	4.842%	$54.0356	$54.04	$54.05	$54.00
Purchase #3	$224.59	4.822%	$235.4197	$235.42	$235.40	$235.40
Purchase #4	$249.50	5.636%	$263.5618	$263.56	$263.55	$263.60
Purchase #5	$228.55	7.410%	$245.4856	$245.49	$245.50	$245.50
Purchase #6	$56.74	8.581%	$61.6089	$61.61	$61.60	$61.60
Purchase #7	$35.43	11.532%	$39.5158	$39.52	$39.50	$39.50
7 purchase totals =	$1,018.12		$1,085.9790	$1,085.99	$1,085.95	$1,086.00